On sunny days, the sunshine warms up bodies of water such as rivers, streams, ponds, lakes and even the ocean. If youve ever watched a kettle in action, you already know that when water warms up, it converts from a liquid to a gas. That gas is called water vapor. This effect happens with water outdoors too, so when it is sunny, the water vapor rises high up in the sky. When a lot of water vapor collects in the sky, it forms clouds.

When water becomes warm enough, the molecules change their state. This helps to transform the liquid to a gas or vapor. The entire process is known as evaporation. It is a very important process in the water cycle because it creates clouds in the sky.

When you look at the sky, you see that clouds come in many different shapes and sizes. Some are thin, wispy clouds, while others are large, dark and heavy. These large, dark clouds are the ones that are overloaded with water droplets. In fact, theyre so overloaded that they have to empty themselves out by raining! The rain falls back into the lakes and oceans, and also into the soil.

Snow looks completely different from rain, but it is actually formed in a similar way. When water rises up into the sky, sometimes the air is so cold that the water particles become solid. Unlike rain, snow cant flow everywhere, so it piles up on the ground. Later, when the temperature becomes a little bit warmer, the snow changes its state once again and turns into a liquid. When it converts back into water, it can move more easily and soaks into the ground. When the air is cold, we dont always get snow. Depending on the weather conditions, we might also get hail, sleet or freezing rain!

In places with mountains, it is very common for a lot of snow to gather on top of the mountains. Since the temperature is colder there, the snow doesnt melt. Instead, as more and more snow falls on the mountain, the pressure and temperature turns it into ice. Sometimes it can eventually also form a glacier. By the springtime, when the temperature is warmer, the ice and snow gradually melt and trickle down the mountain. Sometimes this water might form a stream or river down the mountain, but if theres a lot, it could be a waterfall!

When it rains and when snow melts, the water usually ends up in a stream or river, which flows to the ocean. This means that water travels a very long distance! On very hot summer days, it can become so hot that streams and even rivers have lower amounts of water. In extreme cases, they can dry up completely.

The worlds oceans all exist because of the water cycle. The massive network of rivers and streams around the world feed into the oceans and help to keep them replenished. Even though the ocean is so huge, hot weather can cause some of its water to evaporate. This continues the water cycle over and over again. Around seventy percent of the Earth is made up of water and most of it is in the oceans.